Method and apparatus for applying lubricants to sheet metal



Dec. 18, 1956 A, M FUClNARl 2,774,684

METHOD AND APPARATUS FOR APLYINGLUBRICANTS TO SHEET METAL Filed June l2,1955 /3 T E INVENTOR i Angelo M- Fucinari ATTORNEYS METHOD ANDAPPARATUSOR APPLYING LUBRICANTS VT0 SHEET METAL Angelo M. Fucinari,Detroit, Mich., assignor to The H. A. Montgomery Company, Detroit,Mich., a corporation of Michigan Application June 12, 1953, Serial No.361,174

11 Claims. (Cl. 117-65) This invention relates to dry film type drawinglubricants and methods and apparatus for applying the compositions tosheet metal prior to forming articles therefrom. i

Sheet metal of relatively heavy gauge is subjected to deep drawingoperations under extremely high die pressures in a number ofmanufacturing fields where practically flawless final stampings ofintricate shapes are desired. A serious problem in such deep drawing ofheavy gauge sheet'metal has been to provide proper lubrication betweenthe metal and the dies. Failure to do so results in many difficulties,such as tearing or excessive thinning out of the metal, excessive diewear, and the build-up of lubricant in the dies to a degreesuicient toseriously impair the accuracy of the work. Solution of the lubricationproblem requires the provision of a satisfactory lubricant and apractical method or system for applying the lubricant at some stageprior to the actual stamping operation.

In many cases, it would be desirable to be able to apply drawinglubricants to sheet metal of all gauges well in advance of the metaldrawing operations and to store the coated sheets for subsequent use asneeded. However, this has required an impracti'cally high degree of carein handling the coated sheets, and lthe aging characteristics of thecoatings have generally not adapted them for storage Much progress hasbeen made in devising a number of lubricants that give excellent serviceunder a variety of conditions. However, relatively little progress hasbeen made in methods and apparatus for applying the lubricants.Spraying, dipping, and brushing techniques are commonly employed buthave a number of draw-backs, such as: (l) excessive time, manpower,and/or plant floor space requirements, (2) the necessity for drying theapplied lubricant fil-m and protecting the film during temporary storageor transit to the press, (3) lack of accurate control of the thicknessof the applied lubricant film and (4) the necessity for removingrust-proofing mill oilfrom the sheet metal before applying the drawinglubricant.

Efforts have been made to apply drawing lubricants by means of rollers,but such efforts have had very limited success in eliminating theabove-mentioned draw-backs of other systems. At least, no roller typeapplication systems have yet gone into general commercial use to thebest of my knowledge.

The principal objects of the invention are to provide a process andapparatus for quickly applying a uniform, dry, lubricant film of theproper thickness to sheet metal with reduced manpower and plant floorspace requirements; to eliminate the delays and oor space formerlyrequired for drying the applied lihn; to eliminate the necessity forcleaning mill oil from the metal sheets before applying the drawinglubricant; to provide an improved drawing lubricant adapted to beapplied by such a process and apparatus; to provide a drawing lubricantwhich will produce a hard, durable, non-tacky film capable ofwithstanding subsequent stacking, storage, and handling of the coatedsheets before they are stamped; and to provide a drawing lubricantAwhich satisfies the foregoing objectives and which is also etlicient asa high pressure drawing lubricant, economical to produce, and easy toclean from the stamped product prior to theapplication of finalprotective coatings.

The foregoing objects are accomplished by applying to both sides of asheet of metal,`preferably Aby means of rollers, thin films of a melted,normally solid lubricant. The lubricant7 as applied, and the applicationrollers as well, are maintained about l0 Fahrenheit degrees or so abovethe melting point of the lubricant, but the sheet being coated'is enoughcooler to chill the applied films almost instantaneously to a solidcondition. The applied and solidified films, while still soft enough toow under pressure, are then contacted by finishingV rollers which thinthe filmsv to the desired linal thickness and force them into ymoreintimate contact with the-metal sheet and into the microscopic pores inthe surfaces of the sheet. The temperature of the finishing rollers iscontrolled to further chill the lubricant films to a degree such thatthey are in a hard, non-tacky condition as the Vcoated sheets leave themachine, whereby the sheets may be immediately stacked andthereafter-handled without rdamage to the films. H

The apparatus employed for carrying out the foregoing process preferablyincludes a series of three closely spaced and aligned sets ofsubstantially identical, power driven, cylindrical, steel rolls, wherebya flat sheet may be passed successively between the pairs of rollscomprising the three sets.- The two rolls in each set are suitablymounted for oppositerotation within an adjustable spacing to accommodatemetal' sheets'of various thicknesses. Suitable means are provided for'adjusting the pressure exerted by the rolls on a metal sheet passingtherebetween. Also, means are "provided for maintaining the surface ofeach roller at a desired temperature.

The first set of rolls squeezes olf from the sheets excessive quantitiesof mill oil that may be present and smooths out any major aws in thesurfaces of the sheets, while establishing the temperature of the sheetssomewhat above normal room temperature if required because of a lowinitial temperature of the sheets as fed to the machine. The rolls ofthe 'second set have the melted lubricant spread on their outervsurfaces in any desired manner, and they apply the lubricant to bothsides of the sheets while exerting sufficient pressure thereon tocontrol to some degree the thickness of the applied lms. The rolls ofthe third set perform the above-described finishing functions. L Y

A lubricant capable of behaving as desired during the coating operationsand having the desired final properties preferably comprises a vegetableor mineral oil serving essentially as la vehicle for other ingredientsthat give the compositionthe desir-edz lubricity and general physicalcharacteristics. rlfhe other essential ingredients include awater-insoluble metal soap of afatty acid, a cellulose ether, and a waxylubricating component that is normally solid but plastic under pressure.Also, in most cases, a high-melting point coupler or-mutual solvent,such as an amide of a higher fatty acid, is includedto render thecellulose ether more compatible with -the oil vehicle and to facilitatewashing the lubricant from the metal after the drawing operation hasbeen performed. The proportions of the ingredients are adjustedaccording to their relative melting points, viscosities, and othercharacteristics, mentioned hereinafter, to produce a normally solid,relatively hard and non-tacky, homogeneous mixture having a meltingpoint substantially above the highest atmospheric temperatures likely tobe encountered.

While particular emphasis has been placed above on the suitability ofthe invention for coating heavy gauge sheet metal to be severelydeformed under high pressures, the advantages of the invention are alsorealized in large part in the coating of light gauge metal for any kindof drawing operations.

The foregoing and other objects, advantages, and characteristic featuresof this invention will be more fully understood from the followingdetailed disclosure, and from the accompanying drawing illustrating theessential features of a preferred machine for applying the lubricantcompositions. In the drawings- Figure 1 is a fragmentary and somewhatdiagrammatic longitudinal section of a machine for applying thelubricant compositions; and

Fig. 2 is an elevation of the machine of Fig. l, looking at the left endthereof as viewed in Fig. 1.

The process of the present invention, depending upon the conditions ofprevious storage of the metal sheets to be processed and the meltingpoint of the lubricant to be applied, may or may not require preliminaryheating or cooling ofk the. sheets to bring them to a coatingtemperature in the preferred range of about 70 to 125 F. The coatingtemperature of the sheet should be substantially below the melting pointof the lubricant for chilling the lubricant as it is applied, preferablyat least 50 Fahrenheit degrees below the lubricant melting point, andthis melting point should be appreciably higher than any temperaturelikely to be encountered during subsequent storage of the coated sheets.A lubricant melting point `above 125 F. is desired for nearly allapplications, and a melting point above 175 F. is preferred.

The sheets to be processed are also preferably given a preliminaryrolling operation between pressure rolls to remove surface flaws in thesheets and to squeeze excess mill oil from the sheets. By employingrolls for this purpose that are maintained at the proper temperature,they may also serve to warm or chill the metal sheets through such smalltemperature changes as may be required. Thus, the sheets are preferablypreliminarily conditioned in this manner, the temperature thereof beingthereby adjusted to whatever extent may be required.

The normally solid lubricant, while at a temperature 5 to 10 Fahrenheitdegrees or so above its melting point, is then spread uniformly overboth surfaces of the conditioned sheet. This may be done in any desiredmanner, but most conveniently by passing the conditioned sheet from theconditioning rolls directly between a pair of coating rolls maintainedat substantially the temperature of the melted lubricant and suppliedwith continuously renewed layers thereof for transfer directly to bothsides of the sheets. As so applied, the lubricant films are preferablyspread to an linitial thickness of l to 2 mils, somewhat in excess ofthe desired final film thickness. This may readily be done by suitableadjustment of the pressure of a pair of coating rolls employed for thispurpose, and the lower initial coating temperatures of the sheets servesto chill and solidify the films practically instantaneously.

When employing a lubricant having the proper plasticity, the solidifiedfilm may then be rolled to a final thickness of less than 1 mil,preferablyfrom about 0.2 to 0.5 mil, and chilled to a hard consistencyby passing the coated sheets from the application rolls directly betweena similar pair of pressure rolls maintained at a suitable temp-eraturewhile exerting sufficient pressure to reduce the film thickness andforce it into the microscopic pores in the metal surfaces, withoutpicking up or peeling the films from the sheets. This finishing rolltemperature will vary with the characteristics of the lubricantemployed, but will be well below the melting point of the lubricant andgenerally well above the initial coating temperature of the sheets.Using lubricant compositions of the character hereinafer described, thefinishing roll temperature should be to 75 Fahrenheit degrees below themelting point of the lubricant.

With a preferred melting point between 175 and 205 F., the finishingtemperature will be from about F. to about 185 F. and generally betweenabout 140 and F.

When a properly formulated lubricant composition is employed, the coatedsheets willleave the finishing rolls with hard, non-tacky iilms thereonwhich require no further drying. The coated sheets may be immediatelyhandled and stacked and may be stored before being drawn for periodsthat depend upon the composition of the lubricant.

From the foregoing, it will be appreciated that a suitable drawinglubricant for the purposes of the invention should have the followinggeneral physical characteristics 1. It should be a relatively hard andnon-tacky material at temperatures up to at least 100 F. and preferablyup to about 140 or 150 F.

. It should be mobile under substantial pressure over a wide range oftemperatures below its melting point, for instance down to roomtemperature.

3. lt should have a melting point above at least 125 F. and preferablybetween about and 200 F.

4. It should preferably be a free-flowing viscous liquid at close to itsmelting point, preferably within 10 to 25 F. of its melting point, oreven closer.

5. It should have a high degree of lubricity and a high film strengthunder pressure.

6. It should be compatible with substantial vamounts of mill oil presenton sheets to be coated. 7. It should be stable with age when exposed inthe form of thin films.

Compositions suitable for use in accordance with the invention on steelplates ranging up to 1/2 inch or more in thickness preferably aremixtures of the following principal components in approximately. theamounts designated:

30% to 50% mineral, vegetable, or animal oil vehicle having a viscosityfrom about 100 to about 10,000 S. U. V. at 100 F.

5% to 25% normally solid fatty acid metal soap soluble in the oilcomponent 2% to 15% cellulose ether dispersible in the mixture 8% to 30%normally solid fat, fatty acid, microcrystalline wax, or the like (5% to18% normally solid fatty acid amide as a dispersing or coupling agent,if necessary to disperse the particular cellulose ether employed in theparticular oil vehicle employed.)

ln mixtures of this character, the mineral, vegetable, or animal oilserves as a vehicle and plasticizer for the solid components of themixtures. It also renders the mixtures more compatible with mill oilscommonly present on metal sheets to be coated with lubricant, thusmaking preliminary removal of the mill oil unnecessary. While theviscosity of the oil vehicle may be as low as 100 S. U. V. at 100'F.',employment of a low viscosity oil Vehicle requires the employment ofhigher viscosity additives or greater quant-ities of additives toachieve a suitable final viscosity for application as a thin film withcoating rollers set at about 30 to 60 pounds pressure per inch of rollerlength. The indicated upper limit on viscosity of the oil vehicle (i. e.10,000 S. U. V. at 100 F.) is based on practical considerations and isnot a precise limit. It represents the highest viscosity ofcornmercially available refined mineral oils. For greatest ease ofapplication by rollers, the final viscosity of the lubricant mixture inthe melted condition in which it is preferably applied to the metalshould be about 100 to 300 S. U. V. at the application temperature. Theviscosities of all of the individual ingredients may vary considerably,21S hereinafter noted, and are balanced relativeto one another 4so as toproduce a mixture vhaving a convenient application viscosityat F. or soabove its melting point and having a suitable hardness and degree ofplasticity at temperatures below its melting point. Thus the viscositiesof individual components of the mixture, including that of the oilvehicles, are not in the least critical and are mentioned herein merelyas practical preferences for convenience in formulation.

As noted, vegetable or animal oils may be used in place of mineral oils,in which case the cellulose ether is more easily dispersed in themixture and the fatty acid amide may be dispensed with except for thecleaning off problem noted below. If used, the fatty acid amide permitscellulose ethers of somewhat lower oil solubility to be dispersedwithout difficulty. However, from the standpoint of cost, the mineraloils are preferred over the vegetable and animal oils.

The normally solid metal soap of a fatty acid is employed Ito improveadherence of the composition to the metal and to reduce the tackiness ofthe applied film. It may also serve as an ingredient for increasing orcontrolling the viscosity of the composition for the purposes mentionedabove. Aluminum stearate is a preferred soap. Other metals, such as thealkaline earth metals, zinc, lead, etc., may be combined with stearicacid to form the soap, or other acids having from 16 to 20 or morecarbon atoms may be used in place of the stearic acid in combinationwith either aluminum or any of the other metals, so long as theresulting soap is normally solid and soluble in the oil vehicle.

The principal function of the water-insoluble cellulose ether is toincrease the hardness and melting point of the mixture, to increase theviscosity of the mixture above its melting point, and to reduce thetackiness that otherwise tends to result from bleeding of the oilcomponent out of the solids of the applied film. Care should be used notto employ excessive amounts of cellulose ethers, however, because theytend to increase the buildup of the lubricant in the drawing dies.Methyl cel.- lulose and other water-soluble cellulose ethers are not asuseful for the purposes of the invention as the normally water-insolubleethyl cellulose because the former are less oil-soluble. Higheraliphatic radicals than ethyl may be used in the cellulose ethermolecules, but they also tend to make the cellulose ether more difiicultto disperse in oil and are preferably avoided for this reason, thoughthey may be used more easily with a vegetable or animal oil vehicle. Thepreferred viscosity of the cellulose ether is about 20 centipoises.Higher viscosities, up to lOO centipoises or so may be used, but thisalso decreases oil solubility and requires somewhat more coupling agent.If the oil vehicle is a vegetable or animal oil instead of a mineraloil, ethyl cellulose is amply soluble in `the amounts used without thenecessity for employing a coupling agent.

The normally solid fat, fatty acid, microcrystalline wax, or the likeconstitutes the primary lubricating ingredient of the composition. Theparticular one of these types or classes of lubricant ingredientsemployed will depend on a number of factors, for they differconsiderably in certain properties as will be explained.

Since a hard film is desired, one of the principal considerations isthat the lubricating ingredient be solid (i. e. self-sustaining butplastic unde-r pressure) over the ordinary range of atmospherictemperatures. This rules out of consideration many, though not all, ofthe unsaturated fats and fatty acids per se. In general, any of thenormally solid fats, fatty acids, or mixtures thereof can be employedwhen the metal to which the lubricant is to be applied is to be drawnsoon afterward, i. e. without a long storage period during which thelubricant film may deteriorate from age and atmospheric influences. Suchdeterioration results in large part from the natural tendency of fatsand fatty oils, when held properties indefinitely.

below their. melting points, to crystallize progressively withv time.`vWhen they have crystallized to a substantial degree, they becomeunsatisfactory drawing lubricants because they tend to build up on thedrawing dies, destroying their accuracy and causing excessive die wear.

When ability to-withstand storage periods of more than a relatively fewhours is important, substantially noncrystalline or m-icrocrystallinesubstances have been found to be eminently satisfactory as the essentiallubricating component of drawing compositions contemplated by thepresent invention. Examples of such substances are the normally s olideutectic mixtures of saturated fatty acids, which are uniquely amorphousor non-crystalline in character. As a result of their apparentnon-crystalline character, they retain their waxy and slippery orgrease-like Whereas individual fatty acids and non-eutectic fatty acidmixtures are soft, eutectic fatty acid mixtures are relatively tough andhard, and contribute greatly to the kind of film-forming propertiespreferred for use in accordance with the invention.

According to the literature, only a relatively few of the many possiblebinary and tertiary eutectic mixtures of fatty acids have beeninvestigated in the laboratory. Many are liquids at temperatures too lowto be useful for the purposes of this invention. However, a substantialnumber are suitable, though only a very few are presently availablecommercially. A preferred fatty acid eutectic mixture that is presentlyavailable. from Armour and Co. of Chicago, Illinois, is sold under thename Neo-Fat 1-54. This is a hard, waxy mixture of palmitic acid (67%),stearic acid (29%), and oleic acid (4%), and has a melting point ofabout 150 F. The oleic acid is probably present as an impurity, since itis most difiicult to remove it completely from stearic acid, and themixture should be viewed as being essentially a binary eutectic mixtureof palmitic and stearic acids.

Examples of suitable lubricating agents of the microcrystalline classare the so-called microcrystalline waxes obtained from petroleum. Thesewaxes constitute the higher boiling e'nd of the paratiin wax cut inconventional petroleum fractionation processes, and vary slightly inproperties according to the particular limits employed in separating thepetroleum fractions. These waxes are also commonly known as petrolatum.While the microcrystalline waxes produce excellent formulations for mostpurposes, they are inferior to the eutectic fatty acid mixtures asregards the ease with which the lubricant film may be removed from metalafter the drawing operation, and they require use of hydrocarbonsolvents or the like for effective cleaning.

The fatty acid amides are employed to aid in incorporating the celluloseether into an oil vehicle in which its solubility may. be limited.Depending on the particular oil vehicle and cellulose ether employed,more or less fatty acid amide may be required for this purpose. Thenormally solid amides of fatty acids are preferred over the many othercompounds having comparable coupling properties because such 4amides maybe employed without unduly reducing the hardness of the composition orits viscosity above its melting point. Of the normally solid -fatty acidamides, those melting in the yrange of about to 250 F. are preferred.The amides of saturated fatty acids having 16 to 18 carbon atoms arehard wax-like compounds meltingvaround 200 to 220 F. andare ideallysuited for the present invention, such as those sold as Armid HT byArmour and Co., Chicago, Illinois, which melt at -about 208 F. However,insofar as the present invention is concerned, Vthe fatty acid radicalsof the amides may be either saturated or unsaturated.

While the broad range of ingredients given in the above tabulation maybe considered to represent approximate practical limits for achievingthe objects of this invention, vpractically all needs in drawing sheetmetal may be met with optimum results and minimum 35% to 45% mineral oilof 5000 S. U. V. at 100 F.

20% to 25% aluminum stearate to 10% water-insoluble ethylcellulose, 20to 100 centipoises 8% to 24% eutectic mixture of palmitic and stearicacids (such as Neo-Fat 1-54 manufactured by Armour and Co.)

8% to 15% amide of fatty acids having 16 to 18 carbon atoms and meltingabout 200 to 220 F. (such as Armid HT manufactured by Armour and Co.,Chicago, Illinois).

Example 1 A specific composition illustrative of those embraced by thepreferred ranges of ingredients mentioned above is as follows:

40% mineral oil of 5000 S. U. V. at 100 F. 23 aluminum stearate 8% ethylcellulose of 20 centipoises 16% Neo-Fat 1-54 13 Armid HT Thiscomposition is especially suitable for heavy duty drawing of relativelyheavy steel plates up to about 1/2 inch thick. The composition melts atabout 180 F. and has a viscosity of 200 S. U. V. at the preferredapplication temperature of 210 F. When this particular com` position isto be applied at this temperature, the sheet metal is preferably at atemperature of about 90 to 95 F. as it is fed to the coating rolls. Theoptimum metal temperature will vary somewhat with its thickness and mayrequire some preliminary heating of the metal in winter and cooling insummer depending on the storage conditions. As hereinafter described inmore detail, the temperature of the sheet metal may be established atapproximately the desired initial temperature by passing it between aset of pressure rolls that are either heated or cooled as may berequired.

When the lubricant composition of this example, in liquid form at 210F., is spread as a thin layer on heavy steel plate at a temperaturearound 90 to 95 F., the lubricant is almost instantaneously chilled to asolid but plastic condition and can be immediately rolled to any desiredfinal film thickness by means of a set of finishing pressure rollers,which are preferably maintained at a temperature around 140 to 160 F. toprevent sticking of the coating to the finishing rolls and peeling itfrom the coated sheet. The final film thickness should be around 0.3 to0.5 mil. The lubricant film thus formed is hard and non-tacky as itcomes from the finishing rolls, and the coated sheets may be immediatelyhandled and stacked without additional cooling or drying and A somewhatlower melting lubricant composition suitable for the purposes of thepresent invention is as follows:

45% mineral oil of 5000 S. U. V. at 100 F. 24% aluminum stearate 8%ethyl cellulose of 20 centipoises 8% Neo-Fat 1-54 Armid HT The idealworking temperature of this lubricant for roll application is about 180F. The applied film is softer and more mobile at room temperature thanthe film obtained with the composition of Example 1.

lExample 3 -A harder and less mobile filmv than is obtained with thecomposition of either Example 1 or Example 2 may be produced with thefollowing composition:

37% mineral oil of 5000 S. U. V. at 100 F. 23% aluminum stearato 10%ethyl cellulose 15% Neo-Fat 1-54 15 Armid HT The ideal roll applicationtemperature of this composition is about F.

Turning now to the apparatus shown in the drawing for applyinglubricants in accordance with the invention, it will be observed thatthe apparatus includes sets of pressure rollers that are generallysimilar to those employed for a variety of purposes in differentindustrial arts. To the extent that the structure of the machine mayfollow well-known design principles, many of the details of the machinehave been omitted for simplicity.

A suitable machine may comprise a frame 1 on which three sets of rollersmay be mounted in horizontal alignment for passing a sheet of metal 2along a horizontal path successively between the pairs of rollers of thethree sets. The three sets of rollers may include a first pair 4 and 5for squeezing excess mill oil from the surface of a metal sheet andsmoothing out any major surface flaws in the sheet; a second pair ofrollers 6 and 7 respectively horizontally aligned with the first pair ofrollers 4 and 5 for applying lubricant to the sheet; and a third pair ofrollers 8 and 9 respectively horizontally aligned with the first pair ofrollers 4 and S and the second pair of rollers 6 and 7 for reducing thethickness of the lubricant film and forcing the lubricant into the poresin the surface of the metal sheet 2. Each of these pairs of rollers maybe similarly mounted on the frame 1 in a well-known manner, and only themounting of one pair of rollers need be briefly described.

Considering the pair of rollers 8 and 9, each roller is mounted on ahollow shaft 11 of reduced diameter with respect to the diameter of theroller, the shaft projecting axially in both directions beyond the endsof the roller. Each projecting end of the hollow shaft 11 is mounted forrotation in a bearing carried by the frame 1. The bearing for the lowerroller 9 need only surround the lower half of the circumference of theshaft 11 and may comprise a suitable bearing block 12 mounted on theframe 1 for vertical adjusting movement by means of an adjusting screw13.

The upper roller 8 is preferably mounted at each end by a pair ofbearings that substantially completely surround the circumference of theshaft 11. Each of these bearings may comprise a pair of upper and lowerbearing blocks 15 and 16 mounted on the frame 1 for vertical movement inresponse to the movement of a vertical shaft 17. The shaft 17 may beconnected to the upper bearing block 16 and to a piston in a pressurecylinder 18 adapted to receive fiuid under pressure for forcing thebearings at opposite ends of the upper roller 8 downwardly toward thebearings at opposite ends of the lower roller 9 with a controlledpressure. The adjusting screws 13 permit the elevation of the lowerrollers 5, 7, and 9 in the three sets to be fixed at the desired levelfor accommodating sheets 2 of various thicknesses, and the upper rollers4, 6, and 8 may be forced downwardly with selected different degrees offorce by the application of fluid pressure to the pistons in thecylinders 18. This rolle.r mounting arrangement is sufciently common tovarious types of rolling machines to require no detailed disclosure andmay be constructed in a variety of well-known ways.

The lubricant to be applied to the metal sheet 2 is stored in acontainer 21 that may be mounted in any desired manner on the frame 1above the three sets of rollers. The container 21 is constructed in asuitable manner for controlling` the temperature of its contents, as byproviding a hollow space 22 in the bottom and side walls of thecontainer through which a heat exchange fluid may be circulated.According to the preferred forms of the invention, for most drawinglubricant applications, the drawing lubricant 23 stored in the containeris one that melts in the range of 175 to 205 F. and is applied at atemperature around to 10 F. above its melting point. When employing sucha lubricant, it is not necessary to maintain its temperature in thecontainer 21 above the boiling point of water, and water may constituteand is preferably used as the heat exchange medium in Vthe space 22.Other heat exchange fluids or other heating methods may, of course, beemployed if desired.

Suitable conduits are provided in communication with the interior of thecontainer 21 for feeding the liquid lubricant 23 to both the upper andlower' application rollers 6 and 7. As shown, a pair of separateconduits 24 and 25 may be employed for this purpose, each of theconduits having a suitable, manually adjustable valve 26 or 27associated therewith for controlling the rate of feed of the lubricant.Each of the conduits 24 and 25 is also preferably provided withinsulated coverings 28 and 29 to prevent cooling and solidification ofthe lubricant in the conduits, and the bodies of the valves 26 and 27are preferably located close to or within the container 21 so thatsubstantially all of the lubricant in the conduits 24 and 25 will draindownwardly therefrom when the valves are closed during periods ofidleness.

The upper lubricant applying roller 6 is engaged by a doctor roller 31that is parallel to and axially coextensive with the roller 6 and issuitably mounted for free rotation. The conduit 24 leading from thecontainer 21 terminates directly above the converging surfaces of theoppositely rotating rollers 6 and 31 for feeding the lubricant 23thereto at a controlled rate for maintaining a small quantity 32 of thelubricant between these converging surfaces over the full axial lengthsthereof. The pressure of the doctor roller 31 against the lubricantapplying roller 6 is made adjustable in any well-known manner to controlthe th-ickness of the film of lubricant on the downwardly moving surfaceof the application roller 6.

Another container 35 having two separate compartments 36 and 37 ismounted below the sets of rollers with the lower application roller 7extending into the compartment 36 and the lower finishing roller 9extending into the compartment 37. This container 35 is also preferablyprovided with a suitable space 38 through which a heat exchange iiuidmay be circulated for maintaining the lubricant in this container aboveits melting point and at the desired lubricant applying temperature. Theconduit 25 leading from the upper container 21 terminates at a suitablepoint above the compartment 36 of the lower container 35 for feedinglubricant 23 thereto at a controlled rate for maintaining a lubricantlevel therein above the bottom of the lower application roller 7. Thisapplication roller rotates in the direction shown by the arrow appliedthereto in Fig. l and picks up a continuous film of lubricant from thecompartment 36.-

A second doctor roller 41, similar yto the doctor roller 3l describedabove, is mounted for pressure engagement with the lower applicationroller 7 for reducing the thickness of the film of lubricant picked upby the application roller 7 from the compartment 36. The pressure of thedoctor roller 41 against the application roller 7 causes excesslubricant picked up by the latter to build up between the convergingsurface of the -two rollers to a small extent, as indicated at 42, andany excess flows back down into the compartment 36.

The mechanism for mounting and controlling the pressure exerted by thedoctor rollers .31 and 41 may be any' of the types well-known in the artand has been V'10 omitted for simplicity, since it forms no part of thepresen-t invention. The two finishing rollers 8 and 9, which applypressure to the coated metal sheet 2 as it leaves theV lubricantapplying rollers 6 and 7, may tend to pick up small quantities of thelubricant which must be removed from theV roller surfaces. For thispurpose, a pair of Scrapers 44 and 45 are respectively mounted on theframe 1 for engaging the finishing rollers over their entire length, asshown in Figs. 1 and 2. The scraper 44 associated with the upperfinishing roller 8 removes any i adherent solidified lubricant andcauses it to drop into a receptacle 46 disposed below the scraper 44 andextending the full length of the scraper. The scraper 4S associated withthe lower finishing roller 9 is located so that solidified lubricantremoved from the lower finishing roller slides over this scraper anddrops into the compartment 37 of the lower container 35, where it isremelted by the heat from the heat exchange fluid circulated through thespace 38 in the walls of this container. The receptacle 46 may also beheated if desired so that lubricant received thereby may be remeltedcontinuously and drawn off, or the receptacle 46 may merely be mountedfor easy detachment so that its contents may be, emptied from time totime. The latter procedure is generally satisfactory, since only arelatively small amount of lubricant will adhere to the finishingrollers and require removal by the Scrapers. Both compartments 36 and 37of the lower container 35 are preferably provided with valved conduits48 and 49 for draining the compartments when the machine is to be shutdown or when the accumulation of lubricant in the compartment 37 risesto a level approaching the lower finishing roller 9, which is notintended to pick up any lubricant.

As noted above in describing the method steps of the present invention,it is desirable to establish the sheet 2 at a suitable coatingtemperature by controlling the temperature of the first set of rollers 4and 5. Similarly, it is desirable to maintain the temperature of theapplication rollers 6 and 7 at substantially the desired coatingtemperature of the liquefied lubricant 23 and to maintain thetemperature of the finishing rollers 8 and 9 substantially below themelting point of the lubricant 23 for chilling the lubricant film. Thismay be most easily accomplished by passing streams of a suitable heatexchange fluid, maintained at a suitable temperature, continuouslythrough both of the first pair of rollers 4 and 5, additional streams ofheat exchange fluid maintained at a substantially higher temperaturecontinuously through both of the lubricant applying rollers 6 and 7, andtwo other streams of heat exchange fluid maintained at an intermediatetemperature continuously through both of the finishing rollers 8 and 9.Since all three of these heat exchange fiuid temperatures are preferablybelow the boiling point of water, water will generally be the mostconvenient heat exchange fluid. If desired, it may be supplied from asingle reservoir and pumped therefrom through 3 branching conduitscontaining thermostatically controlled heating elements of any desiredtype for providing 3 separate streams of liuid at the 3 differenttemperatures required. The 3 streams may then be conducted respectivelyinto the rollers of the 3 sets. Any other desired arrangement forproviding supplies of heat exchange Huid at the 3 different temperaturesrequired may be employed. Each streammay be introduced into the upperand`lower rollers of the set for which it is intended through a singleconduit 52 which branches into a pair of valved conduits 53 and 54respectively leading int-o the upper and lower rollers of that setthrough the hollow roller shafts 11 at one end thereof. Fluid dischargeconduits 55 and 56 may project from the opposite end thereof. Inside ofeach individual roller the heat exchange liuid may simply be containedby the rollers themselves so that the uid is directly in contact withthe interior surfaces of the rollers.

In placing the machine in operation, the 3 sets of rollers l1 areestablished at their desired temperature in the manner described above,they are appropriately adjusted to exert the desired pressures onsheetsA of the particular thickness to be processed, and a supply oflubricant in the upper container 2l is heated to the desired applicationtemperature. When the lubricant has reached the application temperature,the valve 27 may be opened to supply a quantity of the liquefiedlubricant to the compartment 36 of the lower container 35 until thelower lubricant applying roller 7 is partially immersed therein. 1iothvalves 26 and 27 may then be set at the proper openings for continuouslyfeeding liquid lubricant to the upperk and lower application rollers 6and 7 respectively. At the same time, power is applied through anysuitable mechanism to rotate all 6 of the rollers at the same speed inthe directions indicated by the arrows in Fig. 1.

Each sheet 2 to becoated with lubricant is then merely passed directlybetween the rollers of each of the 3 sets in succession. The first pairof rollers 4 and 5 perform the desired smoothing operation and establishthe temperature of the sheet while squeezing excess mill oil from bothsurfaces thereof. The second pair of rollers 6 and 7 apply the'lubricant to both sides of the sheet as relatively thin films that arechilled sufficiently by the sheet 2 itself to become solidified, whilestill remaining plastic in character. The third set of rollers 8 and 9further chill the applied films while squeezing them down to the desiredfinal thickness so that the films on both sides of the sheet emergingfrom the machine are hard, nontacky, and uniform.

From the foregoing disclosure, it will be apparent to those skilled inthe art that many variations of the invention may be made as regards theparticular lubricant composition employed and the particular method andapparatus for applying the lubricants, while still employing theprinciples on which the invention is based. It will also be appreciatedthat, by the selection of proper lubricant ingredients and proportions,temperatures, roller pressures, etc., in accordance with thoseprinciples, theinvention is admirably suited for accomplishing all ofthe advantages and new results mentioned in a simple and easilycontrolled manner. Accordingly, the invention is not to be construed aslimited to the particular details of the invention disclosed herein forillustrative purposes except as required by the true spirit and scope ofthe appended claims.

Having described my invention, I claim:

1. A process for preparing a sheet of metal for subsequent drawing,comprising applying to the sheet a film of a lubricating compositionhaving a melting point substantially above the initial temperature ofthe sheet, the temperature of the lubricating composition as appliedbeing above its melting point, and applying pressure to said film bymeans of a rolling surface maintained at a finishing temperature betweensaid melting point and said initial temperature of the sheet forreducing the thickness of the film and forcing it into more intimatecontact with the sheet while chilling the film to accelerate setting toa non-tacky condition.

2. A process for preparing a sheet of metal for subsequent drawing,comprising applying to the sheet a iilm of a lubricating compositionhaving a melting point above 125 F., the temperature of the lubricatingcomposition as applied being above its melting point and the coatingtemperature of the sheet as said composition is applied beingsubstantially below the melting point of the composition, vand applyingpressure to said film by means of a rolling surface maintained at afinishing temperature between said melting point and said coatingtemperature of the sheet for reducing the thickness of the film andforcing it into more intimate contact with the sheet while chilling thefilm to accelerate setting to a non-tacky condition.

3. A process for preparing a sheet of metal for subsequent drawing,comprising applying to the sheet a film of a normally solid andnon-tacky lubricating composition having a melting point above 175 F.,the temperature of the lubricating composition as applied being aboveits melting point and the coating temperature of the sheet as saidcomposition is applied being substantially below the melting point ofthe composition, and applying pressure to said film by means of arolling surface maintained 'at a finishing temperature between saidmelting point and said coating temperature of the sheet for reducing thethickness of the film and forcing it into more intimate contact with thesheet while chilling the film to accelerate setting to a non-tackycondition.

4. A process for preparing a sheet of metal for subsequent drawing,comprising applying to the sheet a film of a normally solid andnon-tacky lubricating composition having a melting point above 175 F.,the temperature of the lubricating composition as applied being aboveits melting point and the coating temperature of the sheet as saidcomposition is applied being at least Fahrenheit degrees lower than themelting point of the composition, and applying pressure to said film bymeans of a rolling surface maintained at a finishing temperature betweensaid melting point and said coating temperature of the sheet forreducing the thickness of the film and forcing it into more intimateContact with the sheet while chilling the film to a non-tacky condition.

5. A process for preparing a sheet of metal for subsequent drawing,comprising establishing the temperature of the sheet at a coatingtemperature in the range of about F. to about 125 F., applying to thesheet a film of a normally solid and non-tacky lubricating compositionhaving a melting point above said coating temperature of the sheet, thetemperature of the lubricating composition as applied being above itsmelting point, and applying pressure to said film by means of a rollingsurface maintained at a finishing temperature between said melting pointand said coating temperature of the sheet for reducing the film to athickness between about 0.2 mil and 1 mil and forcing the compositioninto more intimate contact with the sheet while chilling the film toaccelerate setting to a non-tacky condition.

6. A process for preparing a sheet of metal for subsequent drawing,comprising establishing the temperature of the sheet Iat a coatingtemperature in the range of about 70 to about 125 F., applying to thesheet while it is at said coating temperature a film of a normally solidand non-tacky lubricating composition having a melting point of at least175 F., the temperature of the lubricating composition as applied beingabove its melting point, and applying pressure to said film by means ofa rolling surface maintained at a finishing temperature between saidmelting point and said coating temperature of the sheet for reducing thefilm to a thickness between about 0.2 mil and l mil and for forcing thecomposition into more intimate contact with the sheet while chilling thefilm to accelerate setting to a hard, non-tacky condition, saidfinishing temperature being one at which said lubricating composition issolid but will flow under the pressure applied thereto by said rollingsurface without sticking to said rolling surface sutiiciently to peelthe film from the sheet.

7. A process for preparing a sheet of metal for subsequent drawing,comprising establishing the temperature of the sheet at a coatingtemperature in the range of about 70 to about 125 F., rolling onto thesheet while it is at said coating temperature a film of a normally solidand non-tacky lubricating composition having a melting point of at least175 F. while applying pressure to said film, said pressure beingselected to produce an initial film thickness in the range from 1 to 2mils, the temperature of the lubricating composition as applied beingabove its melting point, and applying pressure to said film by means of`a rolling surface maintained at a finishing temperature between saidmelting point and said coating temperature of the sheet for reducing thefilm to a final thickness between about 0.2 mil and 0.5 mil and forcingthe composition into more intimate contact with the sheet while chillingthe film to accelerate setting to its normal non-tacky condition, saidfinishing temperature being one at which said lubricating composition issolid but will iiow under the pressure applied thereto by said rollingsurface without sticking to said rolling surface sufficiently to peelthe film from the sheet.

8. A machine for applying a drawing lubricant to sheet metal comprisinga pair of substantially parallel, cylindrical, coating rolls mounted foropposite rotation with their cylindrical surfaces spaced for applying adrawing lubricant to opposite surfaces of a metal sheet passingtherebetween, means for spreading said drawing lubricant on said coatingrolls, a pair of substantially parallel, cylindrical finishing rollsmounted for opposite rotation with their cylindrical surfaces spaced forreceiving a coated sheet therebetween from said coating rolls, means forforcing said coating rolls together with an adjustable pressure, meansfor forcing said finishing rolls together with an adjustable pressure,and means for maintaining said coating rolls and finishing rolls atdifferent predetermined temperatures, said last mentioned meansincluding means for passing a stream of heat exchange fiuid at onetemperature through said coating rolls and for introducing a stream ofheat exchange fluid at a different temperature through said finishingrolls.

9. A machine for applying a drawing lubricant to sheet metal comprisinga first pair of substantially parallel, cylindrical, coating rollsmounted for opposite rotation with their cylindrical surfaces spaced forapplying a drawing lubricant to opposite surfaces of a metal sheet,means for spreading said drawing lubricant on said coating rolls, a pairof substantially parallel, cylindrical finishing rolls mounted foropposite rotation with their cylindrical surfaces spaced for receiving acoated sheet therebetween from said coating rolls, the cylindricalsurfaces of said finishing rolls being spaced for engaging oppositesurfaces of said coated sheet, means for forcing said coating rollstogether with an adjustable pressure, means for forcing said finishingrolls together with an adjustable pressure, means for maintaining saidcoating rolls at a predetermined temperature, and means for maintainingsaid finishing rolls at la predetermined temperature substantially belowthe temperature of said coating rolls, said means for maintaining thepredetermined temperature of' said coating rolls including means forpassing a stream of heat exchange fluid at one temperature through saidcoating rolls, and said means for maintaining the predetermined lowertemperature of said finishing rolls including means for passing a streamof heat exchange iiuid at another temperature through said finishingrolls.

10. A machine for applying a drawing lubricant to sheet metal comprisinga pair of substantially parallel, cylindrical, pressure rolls mountedfor opposite rotation with their cylindrical surfaces spaced forreceiving a metal sheet therebetween, a pair of substantially parallel,cylindrical coating rolls mounted for opposite rotation with theircylindrical surfaces spaced for receiving a coated sheet therebetweenfrom said pressure rolls and applying a drawing lubricant to oppositesurfaces thereof, a pair of doctor rolls respectively mounted forapplying said drawing lubricant to said coating rolls, a pair ofsubstantially parallel, cylindrical finishing rolls mounted for oppositerotation with their cylindrical surfaces spaced for receiving a coatedsheet therebetween from said coating rolls, means for forcing saidpressure rolls together, for forcing said coating rolls together, andfor forcing said finishing rolls together with adjustable pressures, andmeans for maintaining said pressure rolls, said coating rolls, and saidfinishing rolls at different predetermined temperatures.

11. A machine for applying a drawing lubricant to sheet metal comprisinga first pair of substantially parallel, cylindrical, pressure rollsmounted for opposite rotation with their cylindrical surfaces spaced forreceiving a metal sheet therebetween, a pair of substantially parallel,cylindrical, coating rolls mounted for opposite rotation with theircylindrical surfaces spaced for receiving a coated sheet therebetweenfrom said pressure rolls and applying a drawing lubricant to oppositesurfaces thereof, a pair of doctor rolls respectively mounted forapplying said drawing lubricant to said coating rolls, a pair ofsubstantially parallel, cylindrical, finishing rolls mounted foropposite rotation with their cylindrical surfaces spaced for receiving acoated sheet therebetween from said coating rolls, means for forcingsaid pressure rolls together, for forcing said coating rolls together,and for forcing said finishing rolls together with adjustable pressures,means for maintaining said pressure rolls at a first predeterminedtemperature, means for maintaining said coating rolls at a secondpredetermined temperature, and means for maintaining said finishingrolls at a third predetermined temperature substantially below thetemperature of said coating rolls.

References Cited in the file of this patent UNITED STATES PATENTS488,025 Norton et al Dec. 13, 1892 1,618,799 Blum Feb. 22, 19271,678,162 Pedersen July 24, 1928 2,257,133 Shoemaker Sept. 30, 19412,374,966 Zimmer et al. May 1, 1945 2,419,132 Friedman Apr. 15, 19472,491,641 Bondi Dec. 20, 1949 A2,614,526 Zaber et a1 Oct. 21, 1952

1. A PROCESS FOR PREPARING A SHEET OF METAL FOR SUBSEQUENT DRAWING, COMPRISING APPLYING TO THE SHEET A FILM OF A LUBRICATING COMPOSITION HAVING A MELTING POINT SUBSTANTIALLY ABOVE THE INITIAL TEMPERATURE OF THE SHEET, THE TEMPERATURE OF THE LUBRICATING COMPOSITION AS APPLIED BEING ABOVE ITS MELTING POINT, AND APPLYING PRESSURE TO SAID FILM BY MEANS OF A ROLLING SURFACE MAINTAINED AT A FINISHING TEMPERATURE BETWEEN SAID MELTING POINT AND SAID INITIAL TEMPERATURE OF THE SHEET FOR REDUCING THE THICKNESS OF THE FILM AND FORCING IT INTO MORE INITMATE CONTACT WITH THE SHEET WHILE CHILLING THE FILM TO ACCELERATE SETTING TO A NON-TACKY CONDITION. 